Questions From My Wife V: Color Evolution

What is the point of hair and eyes coming in different colors? I get the evolutionary reason for different skin shades, but not the hair and eyes.

Actually, the genetics of skin color is very complex and is not yet fully understood. So far 4 genes regulating skin color have been identified, and there may be more yet to be found. There are a few theories for the diversity of skin color, such as the balance between avoiding exposure to ultraviolet radiation and production of Vitamin D. Darker skin has the advantage of blocking UV rays and reduced instances of skin cancer due to increased presence of melanin, but lighter skin lets in more light, which is crucial for the formation of vitamin D. Thus areas with less direct light, such as around the poles, have lighter pigmented skin.

However, many scientists view this idea as too simplistic, as it has obvious flaws. People living in the same latitudes -- the Australian aborigines and the Amazonian tribes; the Inuits and the Swedes -- have widely varying skin coloration. Plus most cancers are rarely factors in evolution -- most cellular damage is done far past prime reproductive age. Even Darwin didn't think natural selection had anything to with geographic variations of beauty traits. Current theories are returning to the viewpoint of Darwin and suggesting the evolution of skin color has more to do with sexual choice and picking partners by physical traits that happen to be socially important, but not much else.

Questions behind variations of eye and hair color are very similar to this. Sure, it could have happened for a reason. Legitimate scientific evidence exists that suggests the color of the iris shapes the ability to see in certain light conditions. But while it is more comforting to assume natural selection is involved, it seems more likely that it is not.

Sexual selection is a complicated theory, and not only attributed by Darwin to be the basis of racial differences, but also the general hairlessness of humans and possibly the creation of humor, music, and art. One theory by John Maynard Smith suggests that the human brain was created to its cumbersome levels by sexual selection -- very much like the plumage of a male peacock.